1. Field of the Invention
The present invention relates to an optical deflection device. More precisely, it relates to a holographic deflection device by which the deflection angle can be controlled only by controlling the wavelength of the light beam source and in which it is not necessary to move the lens.
2. Description of the Related Art
In conventional optical deflection devices, the deflection angle is usually controlled by a mechanical displacement of a rotating polygon mirror or an oscillating mirror by a motor. It is also known to use a hologram scanner in which a hologram is mechanically moved.
In these types of known optical deflection devices having mechanically movable portions, the devices are relatively large, lubrication of the movable portions is necessary, and unavoidable wear of the movable portions occurs. Also, the precision of the control of the deflection angle depends on the limited mechanical precision of the mechanical movable portions. The scanning speed is limited by the mechanical movement.
Also known is an optical deflector which incorporates a solid element, such as an acoustooptic element, but this optical deflector can realize only a small deflection angle and thus has only a limited use.
In view of the above, and contrary to the usual practice of the prior art in which it is considered that the deflection angle can be controlled only by a mechanical displacement of a lens or a mirror, the inventors of the present invention decided to investigate a non-mechanical control of the deflection angle.
Namely, the primary object of the present invention is to provide an optical deflection device by which the deflection angle can be optically controlled without moving the lens or mirror.